To examine the relationship between hospital volume and mortality in pediatric leukemia, particularly the at-risk ages of adolescence and young adulthood. Aim1: Examine the association between pediatric oncology volume and adjusted case fatality rates in induction in pediatric acute leukemia (ages 0-15 years). Aim 2: Examine the association between overall pediatric volume and adjusted case fatality rates in induction in pediatric acute leukemia (ages 0-15 years). Aim 3: Examine the associations between a) overall pediatric volume, b) pediatric oncology volume with adjusted case fatality rates in adolescent and young adult (AYA; ages 15- 29 years) induction therapy for acute leukemia. Relevance: In accordance with AHRQ's commitment to improve the quality and effectiveness of health care, the relationship between volume and outcome in pediatric and young adult leukemia will identify likely groups of institutions with high and low mortality. Identification of these clusters will alow for further work to determine the etiology of the variation of mortality between institutions and identification of best practices at low mortality institutions. Methods: We will conduct a multi-sie cohort study using two comparative administrative databases: Pediatric Health Information System (PHIS) and Premier Perspectives Database (Premier). We will identify all newly diagnosed ALL and AML patients from PHIS and Premier, and ascertain in-hospital mortality during induction therapy. Primary adjusted analysis will be undertaken using mixed effects logistic regression model taking into account the clustering by hospital. Research Training Plan: This applicant will conduct all aspects of the specific aims from design through statistical analysis for additional experience in design, data quality and analysis and preparation of future studies. Additional expertise will be developed through coursework in outcomes research and systematic review and meta-analysis in preparation for submission of a Mentored Career Development Award (K-23).